Endothelial Localization of Receptor Tyrosine Phosphatase, ECRTP/DEP-1, in Developing and Mature Renal Vasculature

Developmental assembly of the renal microvascula- ture requires spatially and temporally coordinated migration, assembly, differentiation, and maturation of endothelial cells in the context of adjacent epithelial and mesangial cells. In this study, endothelial expression and distribution of the receptor tyrosine phosphatase ECRTP/DEP-1 were evaluated during and after developmental assembly of the renal microvascula- ture. Monoclonal antibodies against ECRTP/DEP-1 ectodo- main epitopes localize its expression to membrane surfaces of endothelial cells in glomerular, peritubular capillary, and arte- rial renal sites of mature human and murine kidney. During kidney development, ECRTP/DEP-1 immunostaining is evi- dent on a subpopulation of metanephric mesenchymal cells and on putative progenitors of glomerular capillary endothelial cells early in their recruitment to developing glomeruli. ECRTP/DEP-1 is prominently displayed on luminal membrane surfaces with punctate accumulations at inter-endothelial con- tacts that overlap with vascular endothelial-cadherin staining. ECRTP/DEP-1 is recruited to inter-endothelial contacts in con- fluent cultured human renal and dermal microvascular endo- thelial cells, yet experimental dissociation of vascular endothe- lial-cadherin from endothelial junctional complexes fails to redistribute ECRTP/DEP-1. These findings indicate that ECRTP/DEP-1 is expressed in anticipation of glomerular cap- illary endothelial recruitment during development, and suggest that ECRTP/DEP-1 ectodomain interacts with endothelial sur- face ligands that are engaged by cell-cell contact.